With conventional force-based seismic design, the most important information for the structural VEd#LSh
engineer has been the effective peak ground acceleration. This number is comparatively O0"i>}g4
insignificant in displacement-based or performance-based seismic design, where the key data are {KL<Hx2M
peak spectral response displacement, and the “corner” period at which this occurs. There appears (Jf i 3 m
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, &Ko}Pv
which the structural engineer views with concern, since ductile structural response will often be in v&(X& q
this region of the corner period. Dependable information on the reduction of displacement )2oWoZ vi9
response with damping or ductility is also needed for design approaches utilizing secant stiffness w\Q3h`.
characterization. Other areas needing clarification include the issue of how to develop [E(DGt
accelerograms for time-history analysis compatible with the design seismicity using an acceptably !^ 6x64r
small number of accelerograms, and how to reconcile the statistical nature of seismicity
-p>KFHj6
characterization with the structural engineer’s preference for deterministic analysis. There is some +a sJV1a
evidence that a consequence of this is invalid averaging of response characteristics by structural 3V`K^X3
engineers.
